Lake Keeper Report

October 2011

Don Mayland

We are in our third year of the sampling program, which was originally planned for three years.  Each year has been very different, weather wise.  The first year was cool and wet in the summer.  Last year was hot and dry and this past year was a lot of everything...some dry spells but lots of heavy rains.  It is interesting that the different weather conditions did not affect the readings about the water all that much.  The cool wet spring this year did mean that surface temperatures lagged the other years, until we got into late June...then they all look about the same.  Peak temperatures on the surface occur in late July and early August.  This year, as with the two previous years, the dissolved oxygen levels dropped below 6 Mg/l in the bottom waters of the small and large basins in early June.(6 Mg/l is kind of the bench mark for anoxic waters).  The thermocline did not set up quite as early this year, but once it did temperatures were consistent with the two previous years.

   

The greatest interest is probably about weed growth.  This year we had a resurgence of milfoil.  It has been worse in the past, but clearly the cycle is in a phase of increased growth, at least for a few years if it goes as before.  I did a dive last week and did not see a large Caddisfly larvae population, which are the drivers of the cycle.  Chara and other carpeting native weeds are abundant and are helping, to some extent, to keep milfoil at bay.

   

This year, in addition to our normal water quality sampling we also did an inventory of invertebrates (mussels, snails, and crayfish) and zooplankton and phytoplankton.  All of this will be presented in the written report at the end of the year.

   

Visibility readings were poor in the early summer but at the end of August, continuing to the present, the visibility is excellent.  We are getting secchi disk readings in excess of 4 meters, which is much better than the first year of sampling.  Again, reasons for this will be covered in detail in the full report but it is fair to say that the plankton population is the source of visibility changes.  What was interesting was that I sampled the day after Hurricane Irene and, despite the dramatic rise in the water level; none of the readings I take were affected.

    As to the future:  I will be putting the three year figures together in a user friendly report during the winter months. It is true that the more monitoring we can do in the future the better.  But, to sample and monitor 15 or more times in the spring, summer and fall probably isn't necessary. But, to stop monitoring all together would be really foolish!  Why build this data base to use as a comparison if we don't get figures to compare it with?  I suggest that we reduce the monitoring to 3 times once in April, after the ice is out and before the lake stratifies, once in late July when the thermocline is pronounced and one more time right after it de-stratifies in late October/early November. Also, we don't have to produce an extensive report every year after this year.  We do need to keep up our guard, however. Hopefully our partners in this monitoring process will stick with it if the cost is dramatically reduced.

If all we are doing is sampling and not having to construct a large report then it should be less than $2000.  The major costs, besides time spent are fees to the lab for P samples and consultation with a limnologist.  I assume that Hotchkiss will continue to let me use their instruments and boat. I can provide a boat but the instruments are critical.

Just as a point of information;  Marvelwood School schedules every Wednesday morning as a community service time for their student body. This fall I have been working with 5 students.  They help me with sampling and I teach them something about aquatic biology....rewarding for all concerned..I hope.  Hotchkiss students may be helping me this year with the graphing of data that I want to be able to include in the summary (of all 3 years) report